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Mill Town posted:My advice would be to put the dimmer knob in the body of the heat gun, attached directly to the heating element. Then hook the power cord up to the element/dimmer combo in parallel with the fan. Get rid of the existing circuit board entirely. And put the new, bigger dimmer in the line side, not neutral. When your 600W burns out, your board and whatnot will be energized while you're attempting to figure out what went wrong.
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Jan 29, 2009 13:28
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ANIME AKBAR posted:I've got a decently interesting request from the guy I'm consulting for. He wants to make a low power logging anemometer that can measure the flow rate of air at various points in an industrial building. There's a guy balancing all the ducts in the HVAC system right now. The device he uses is a differential pressure system with temp and humidity sensor. There's a perforated tube that goes in the duct and another that's outside the duct. It calculates flow rate from air mass (based on humidity and temperature) and duct area. For places that don't have a duct (like the gym) the device sits in a collapsable nylon duct thing. This is the one he's got. (Click on "products").
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May 5, 2009 12:21
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scuz posted:Soldering iron/station question: I have a metcal that's completely tits. It will solder large bulk metal structures, and with a 3-second tip swap will go straight into soldering very fine SMDs. I kinda wish I'd been able to get the two-tip model, since the second tip controller will work a solder sucker, but such is life.
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May 29, 2009 08:58
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Slung Blade posted:Yep, exactly. Old joysticks are either 0-5k or 0-15k; My throttle is a 0-5k 90 degree pot.
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Aug 6, 2009 04:00
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Why not a circuit that switches on an FM transmitter and signals the receiving computer to switch to the correct frequency? Do as much of the audio in analog as possible and just use the controllers for advanced following and multiplexing. I don't know what the FCC has to say about unlicensed FM transmitters, though.
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Aug 7, 2009 02:42
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Shazzner posted:Hey I've got a question for you guys, I've got some solar panels that are supposed to be used for a car battery, 12V. There would be a problem. Your battery is probably 24V. Two panels in series would probably work OK.
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Sep 3, 2009 02:35
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jovial_cynic posted:edit: aha. After a more careful look at ohm's law, I believe that because I have a constant 12-14 volts, and a known resistance range (22 to 88 ohms) on the fuel sending unit, what my bar-graph LED gauge should be reading is the current, which is a bit easier to figure out. Hooray for hours of researching instead of simply waiting for somebody to tell me the answer. You can also wire a close-tolerance sense resistor in series with your tank sensor and measure voltage across that.
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Sep 20, 2009 20:02
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You need some diodes. When your motor stops or switches direction, it becomes a generator which is backfeeding your network.
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Oct 1, 2009 07:26
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Powdered Toast Man posted:I do not, however, have a frequency counter. I do have a very nice, recently cleaned up and refurbished oscilloscope (it's a vintage Heathkit with a ton of nifty features), and a good digital multimeter (Fluke, unfortunately it doesn't have frequency measurement). There's a grid, right? Time on one axis, voltage on another? Count the peaks on the grid, divide. Frequency.
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Oct 15, 2009 21:01
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thepedestrian posted:So I know very little about electronics, but I'd like to build a proofing box for rising bread. Just an enclosed box with a heat source (I'd use a heat lamp probably) that maintains the temperature it's set at. It's been hard keeping my house warm enough to rise bread in any reasonable amount of time. My brother just put a low-wattage incandescent bulb in the box. 40W, I think for a U-Haul "Medium Box." Failing that, you can get a Thermostat.
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Dec 16, 2009 04:43
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PilotEvan posted:Well I went out and got an AC/DC converter, and although I couldn't just find a straight up 9V one I was able to find a bunch of "universal" ones with variable voltage. This obviously makes the whole thing a whole lot easier since I can set the voltage to an even number, set the number of LEDs in series to Vsource/2 LEDs, and not even worry about resistors at all. You got lucky and your universal voltage thingy sucks. Without resistors and a good power supply, you would have burned out your LEDs. Always include resistors in case something isn't exactly 100% to spec so you can't get massive overcurrent in a leg and burn something out.
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Dec 17, 2009 14:36
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So I got this electric scooter that uses (apparently) a Hall Effect throttle. It's all kinds of messed up from a previous owner. After lightly disassembling it into the shattered bits inside the shell that the last guy left it at, I see what appears to be a metal ring with a transistor mounted next to it. The rotating part of the throttle moves some magnets around the ring. I can get the scooter to move and the throttle to actuate by waving the transistor thing around in free space. Loosely attempting to re-mount the throttle in its correct configuration makes the scooter regulate its speed somewhat, but not predictably. How do I make a new throttle, or how do I fix this one? What kind of signal is a "hall effect throttle" sending? Should I be doing a voltage- or current-controlled signal?
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Jan 4, 2010 01:08
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Otto Skorzeny posted:If it uses a hall effect sensor like the one sparkfun has in stock this may be helpful Nope; as far as I can tell it's an analog device. A digital-latch throttle WOULD be fun, though.
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Jan 4, 2010 01:42
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Metajo Cum Dumpster posted:Beginner question; Why on my cheap MM on the 10amp setting does the current reading continually drop while taking a reading? You're draining the battery and the voltage is sagging as it heats from a dead short. "Regulated" wall-warts aren't, particularly. It's probable that the voltage on that didn't sag too much as the amperage dropped, but those are usually rated in VA and regulation range, which dead shorts usually drastically exceed.
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Jan 8, 2010 14:39
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BattleMaster posted:I think the only PIC18s with two UARTs are in the PIC18 J-series, which are 3.3 volt only. None of the lesser PICs have two and many of the 16- and 32-bit ones do but are also 3.3 volt only. MAPS lists a fair pile of pic18Fs, 2-5.5V with 3PWMs and 2 A/E/USARTs. It lists individual parts for about $3-4 or so. Some even come in 28-pin SPDIP (.070 pitch DIP).
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Jan 12, 2010 05:57
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I recently brought a 48v scooter back to life with four new 12V SLA batteries. I only own a 12V charger, but the batteries are hooked up in series to 48V. I would like to manufacture a 48V charger. Is this feasable? SLA batteries need to be on constant-current charge until per-cell voltage is at a certain point (depends on temperature), then on constant-voltage charge until current drops below a certain point, then on a float charge indefinitely. How should I go about this? Is a 48V power supply doable? I was just thinking a transformer and full-wave rectifier to get to 48VDC, maybe a filter cap to smooth ripple somewhat, then a linear regulator to get to 5 or 3.3V to power a PIC with a temperature, voltage, and current sensor. Any ideas on how to get a 48V signal into a 3.3 or 5V PIC besides a voltage divider? How should I rig a current sensor? What's the best (1 degree accuracy) temperature sensing solution for under $8? Any big gotchas that might loom out of the darkness to blow this thing up?
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Jan 31, 2010 06:14
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clredwolf posted:Yes. Invest in some power resistors before you start testing on/blowing up SLAs though. quote:That'll work. Most SLA chargers I've seen don't actually use the temp. sensor. A switching supply will use less energy, however I'd suggest looking at getting that as a self-contained module and NOT a DIY, switching supplies are not for the feint of heart. quote:Battery? Transformer off the A/C line? I mean you're not gonna get a thunderbolt to the head for having two plugs for this type of thing (just buy another power strip). quote:Three words: isolated sense resistor. Look at using a sense resistor, and an isolated amplifier like an iso 124 (expensive, but worth it for not shocking yourself). Some really rugged opamps can do it too, but you'll need to still isolate it somehow. I've got some 32gauge magnet wire and a couple of 1.000 ohm precision resistors. Is winding my own CT a good solution? Do CTs work on DC? quote:Note sure here, there's a lot of temperature sensors out there though. Sometimes you can work with funky configurations until something falls out that works well (whetstone and kelvin bridge configurations can be extremely accurate). quote:Overvolting the batteries, reverse polarizing the batteries (it WILL happen, how will you fix it?....hint: it can be a pretty easy fix), shorts...any time you work with things over 5-12 volts you have to be mindful of what you are doing. Respect the machine, for it can be dangerous. I'm all about safety. I've got some DIN-rail 120V AC/DC breakers available for pretty cheep. I'm a commercial electrician as my day job. 48VDC at 5A is nothing compared to 480VAC @ 2000A, but that doesn't mean it's safe to play with. You can weld fairly easily with one of these small batteries. The last concern is cost: A 48V smart SLA charger costs about $100-200. I'd like to get this done for around $20 or so. I've already got the PIC and a few precision resistors. I'll scrounge for power resistors for testing, and scrounge for things like filter caps and the like. I've got a k-type thermocouple available, but it doesn't look like it's able to directly interface with a PIC. I think I can also dig up some opamps from some old projects, maybe even a couple of SPI ADC/DACs. babyeatingpsychopath fucked around with this message at 00:01 on Feb 1, 2010 |
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Jan 31, 2010 19:51
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Allistar posted:Hey guys! Ok. So, 48V charger seems like it's gonna be a huge pain in the rear end so how about this: A bank of 3-way switches (SPDT). I realize it's possible to connect the switches in such a manner that there's bad voltage on the rails, but that shouldn't matter as long as I flip all the + terminals first, then all the - terminals. Is there a better way? I'm trying to get out of this cheap; and 3-way switches are about a dollar each. On the other end of the spectrum is a 48V smart charger for $125.
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Feb 14, 2010 02:40
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lurklurklurk posted:Kinda cross-posting from Hardware/Software thread: Hopefully, your system works just like this, and you'll be able to monitor the difference in phase on your sender. The thing to note is that synchros are really rate-driven devices since the receiver starts moving as soon as there's a change. A constant phase offset means constant rate-of-change of input. Of course, if you disconnect the receiver coil, then it's back to an absolute position encoder.
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Feb 18, 2010 14:52
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lurklurklurk posted:Sounds like all I need is the phase and not the amplitude, which would be nice, but it think mine is a little different. I believe there are 4 coils per end, one on the rotor which moves and 3 static at 120 deg intervals around the rotor. This ought to complicate the matter a little more, but if yours were all phase then mine should be too. Sounds like you've got 3-phase coils. The ones I worked with used one phase to energize and had a 3-phase takeoff for higher directional sensitivity. It should give one signal 120 degrees out on three wires, and a three-phase rotor on the needle end. This is a more fail-safe configuration as you can lose either an energizing or rotating coil (sending/receiving) and still have 240 degrees of indication, possibly up to 300 degrees depending on whether the coil or connecting wire failed open or shorted.
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Feb 19, 2010 00:53
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Hillridge posted:Any of you know of a good solar energy forum? I'm planning a 5kW array for my house and want a good place to bounce around some ideas. Make a thread; I've been studying it pretty hardcore from a professional installer's standpoint. I've got a whole slew of tools that (theoretically) can size everything from the panels to the switch/batteries/inverter/etc.
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Feb 25, 2010 00:42
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Aluminum Record posted:Aye, I knew about some of those things (we learned about the resistivity of materials, calculations involving it, and drift velocity of electrons and such. I just wanted to make sure I had the right idea in that the electrons are actually flowing from negative to positive terminals on the battery. Yep. There are two ways of teaching electricity: Conventional current flow and electron flow. Conventional current is + to -, electron flow is how electrons move, - to +. Both work just fine; the sign just comes out different when doing current calculations.
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Mar 1, 2010 05:13
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ante posted:You'll also never use electron flow outside of a physics class. My Electrician's Apprentice course is teaching electron flow for some reason. Made semiconductors really confusing being that I'd learned everything in conventional flow, so all the arrows were pointed all crazy. In other "release the smoke" news, I repaired my wife's electric roasting pan. I'd left it on overnight and burned out the heating element. I calculated the resistance of the old element based on the wattage given. then I went to McMaster Carr and looked at their nichrome wire. Selecting one, I found the resistivity and density of the alloy, then calculated the correct length, and therefore weight. I bought a spool of the right size and some mica tape, and made my own heating element. It works great, now that it's burned in; the wire ships with some kind of oil on it.
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Mar 1, 2010 06:23
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orange lime posted:Does it say anything about current requirements? I'm not an engineer, but I can't see a 9v battery having enough power to do what I think it's doing. That's the point. You don't want much current. Stator current/voltage generates output current/voltage. Low DC input=low AC output. It's just trying to diagnose the problem in the exciter circuit.
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Mar 19, 2010 03:17
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Shazzner posted:Ok I have a really dumb question to ask; I'm only asking this because as I'm learning EE lately a lot of conventions I knew turned out to be completely wrong. If you're lucky, your controller will have a nameplate that gives either VA (volt-amps) or Watts somewhere on it. Size your fuse at 25-50% over that, and your switch interrupt rating at 2x your fuse, and you'll be good. I bet a 5A fuse and a standard residential toggle switch ("light switch") will be fine. Knife switches are usually rated in the hundreds of amps, even for small ones, so that'd work, too. I saw some fused knife switches at the supply house with 140A fuses in a 3" switch.
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Mar 26, 2010 18:57
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dxt posted:I'm trying to make a 60V DC power supply for using a wall outlet to charge batteries and I'm not sure how to get to 60V after rectifying with that square root of 2 factor. Any ideas? Wall power should be 120V RMS, or 170V pk-pk. It should rectify to pretty close to 60VDC.
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Apr 2, 2010 00:32
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dwoloz posted:I'd like to build a wind turbine soon and was wondering if I had an AC generator, could that be directly connected to my utility power to feed back to the grid or do I have to get a DC generator and then use a grid tie inverter Swing on over to the "Don't Burn Your House Down" thread, as we're talking about connecting generators right now. In short, your generator needs a synchronizer to get it to match the grid "well enough" as defined by your power company. It has to be within tolerance on frequency and voltage, and then synchronized with respect to phase. This stuff is not cheap.
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May 1, 2010 19:26
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dv6speed posted:That would seem like the sensible thing huh? A rotary phase converter is a 3-phase generator hooked to a single-phase motor. The output looks like any other 3-phase generator waveform.
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May 4, 2010 00:43
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Frobbe posted:i'd guess that would be the basic operation of the thing, yeah, to me it just seems like it should be hella more complicated than it actually is? Think about it thus: You are switching both the power and the ground connection. If you want to go one direction, this is two switches. Add two more switches to go the other way. Close all four switches and have two short circuits around the motor!
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Jun 7, 2010 19:20
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nobody- posted:2. What's a good book that goes over basic electronics? I'm talking transistors and op-amps, mostly. I've had the standard Physics II classes in college that cover Kirchhoff's laws and basic RC circuits, but I'd really like to have a better understanding of analog electronics. I can kind of put together a circuit that does what I want if I treat it as a bunch of functional black boxes that I can assemble together into a working whole, but there are still massive gaps in my knowledge when it comes to the actual operation of semiconductor devices, and often times, I find that components don't necessarily behave as I thought they would. Are there any books out there that, while explaining theoretical concepts, also show practical applications of this theory? "Timers, Op-amps and Optoelectronic Circuits and Projects" By Forest M. Mims III. Get it from Radio Shack. It's a fabulous book.
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Jun 26, 2010 15:32
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Delta-Wye posted:Disclaimer - I'm a digital guy through-and-through, and sometimes power throws me for a loop. It's embarrassing, but there ya go. Incorrectly wired. That's a standard 50-amp receptacle there. The three blade terminals are y, w, x, from left to right. "W," in the center, is neutral. Should be 0v to ground, and "115V nominal" to the other two, which means 110-120V. RV Power is single-phase from a center-tapped transformer, with the center tap as neutral, so the other terminals SHOULD be reading 220-240V between them. 60V phase-to-phase and 110V to neutral means Something Is Wrong.
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Jul 7, 2010 13:06
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I got my TI 430 Value starter kit today! It's a really powerful little device for the $4 I spent. Now, what to automate? Every coffee machine in the house? RFID Cat Door? Auto-tracking nerf guns?
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Jul 16, 2010 23:51
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Ola posted:Yeah, I need to account for the fact that some gears use only two segments and others five. I'll try to read up on segment drivers, that will probably be much more elegant. Worst case I can get a spare gear position indicator for $15 on eBay but that would be a lot less cool. Lessee... AND/NOR gates feeding 7-segment driver, I think. Lemme try to fab up a pretty simple circuit. This doesn't need a microcontroller AT ALL. edit:  4511 CMOS 7-seg. 22V allowable input. The display should say '0' for neutral/between gears, then 1,2,3,4,5. babyeatingpsychopath fucked around with this message at 04:22 on Aug 12, 2010 |
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Aug 12, 2010 02:21
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Mill Town posted:I think you need to reexamine your diode logic there. The way that's currently set up, 1st, 3rd, 4th and 5th will all display 7, and 2nd will display 0. I think this is what you were going for: Heh. I did, indeed, put the diodes on the wrong side of the connections. I was distracted doing other things.
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Aug 13, 2010 03:02
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ante posted:In other news, my MSP-EXP430 came today! What should I make? My msp430 came a few weeks ago, and it's 100% incompatible with linux. Oh well. Check Radio Shack for the Parallax RFID readers. They've been discontinued, and ring up at $9 (or less), even though the drawer says $49.
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Aug 27, 2010 02:12
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Zuph posted:Careful about that: http://hackaday.com/2010/08/11/how-to-launchpad-programming-with-linux/ Son of a bitch. Stop checking hackaday for a week and look what happens. I even hacked the ti_5280_3140 driver and firmware to get it to recognize to no avail. Ok. I'll try it now with the new tools.
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Aug 28, 2010 02:20
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polyfractal posted:Is there a way to discharge a capacitor/circuit if you can't access the leads to the capacitor? Everything I've read says to discharge a cap by connecting the leads to a big resistor. I'm repairing a Rear Projection TV and don't really want to gently caress around with it until the big cap (120v 1000uF) is discharged...but I can't get to the capacitor leads unless I gently caress around with the TV to remove the board. Catch 22 here I thought modern electronics were required to have bleed resistors on caps. 5 minute discharge maximum, IIRC.
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Sep 16, 2010 01:02
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ante posted:You can use the water-in-pipes analogy. Instead of pumps, think of the batteries as water tanks. The top of the tank is +, the bottom is -. The water level in the tank is voltage. Since both your tanks are at the same voltage, then the water is at the same level. If you connect the top of one tank to the bottom of the other, no current flows because the water level in both tanks is the same.
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Sep 25, 2010 01:06
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Popete posted:Right say you stacked them on top of each other they don't discharge because they are essentially both full? Creating one larger voltage/tank of water. They don't discharge because there's nowhere for the water to go. Two tanks, sitting on top of each other. Nothing connected to the outlet. No current.
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Sep 25, 2010 02:46
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catbread.jpg posted:What's the deal with this? If it's anything like incandescents, then the ripple means they light up, and the filaments stay hot, yet total power output is lower, so life is longer. Lower RMS power, same effective brightness.
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Sep 30, 2010 23:33
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